More important than the inaccuracies (and makeup malfunctions) is what “Mandela: Long Walk to Freedom” (which stars Idris Elba) erases. Among its elisions are the Cold War, communism (the South African Communist Party recently confirmed that Mandela was indeed a member, which had been something of an open secret for years), U.S. support for apartheid and the apartheid state’s sponsorship of so-called black-on-black violence in the 1980s and early 1990s. (In the film, it seems that Winnie Mandela, painted as an irrational, Lady Macbeth–like character, was the cause of the violence, which in fact resulted from clashes between forces aligned with the African National Congress and state-funded proxy organizations like the nominally Zulu nationalist Inkatha.)